The neurochemistry, chemistry and stereochemistry of cholinergic systems is unknown. Cholinergic enzymes are classified by their substrate kinetics, cholinergic receptors by their neural responses. Cholinergic transmission is critical to mental and physical health, yet its study is limited to classical methodologies. This proposal for research is concerned with the design, synthesis and application of new, spectroscopic research tools, and to new methods by which the comparative stereochemistry and physiological actions of cholinergic systems can be studied. It is based on the study of a variety of spectroscopic changes which can occur when certain acridine derivatives are in dynamic equilibrium with cholinergic enzymes and receptors in vitro and with cholinergic neural systems in vivo. The crux of this research lies in its comparative spectroscopic study of the dynamics of interactions of specific spectroscopic molecular probes with cholinergic enzymes and receptors. Extension of the research can include histological and electrophysiological applications of these new fluorescent probe molecules.